First-order vs. second-order structural validity of the Health Literacy Scale in patients with diabetes

The purpose of this study was to determine the structural validity of the Health Literacy Scale (HLS) in Korean patients with diabetes based on the previously reported first-order three-factor and two-factor models and a newly proposed second-order model, to identify which model best represents the structure of the Korean version of the HLS (HLS-K).

The HLS was translated from Japanese into Korean using a translation and back-translation technique. A secondary data analysis was used to validate the structure of the HLS. Data were obtained from a cross-sectional survey involving 459 adults with diabetes recruited from outpatient clinics at two university hospitals in South Korea. The structural validity was examined using confirmatory factor analysis. Additionally, the known-groups validity by education level and internal consistency validity were assessed.

The second-order three-factor model of the HLS-K exhibited a good fit to the data, as indicated by χ² /df = 3.891, SRMR = 0.042, GFI = 0.924, RMSEA = 0.079 (90% CI = 0.069-0.090), and CFI = 0.962. The second-order three-factor model empirically demonstrated that both communicative and critical factors explained the variance in the overall health literacy better than did the functional factor. The HLS-K mean score was significantly lower for patients with only elementary school education than for those with higher education levels, implying the presence of known-groups validity. Cronbach's alpha for the total scale was 0.90.

This study found that the second-order three-factor model of the HLS-K is better than that the original first-order three-factor and first-order two-factor models. Further validation studies are needed to generalise the underlying structure of the instrument in diabetes populations across various cultures.